Sugar testing



Patented July 1, 1930 PATENT OFFICE ABRAHAM G. SHEFTEL, OF NEW YORK, N. Y.

SUGAR 'rnsrmc Ito Drawing.

This invention relates to tests for sugar, particularly tests for sugar in urine.

Since the discovery of insulin, the treatment of diabetes has advanced tremendously. Insulin, in addition to being a successful remedy, proved to the general practitioner and to the diabetic patient the importance of calculated diets, combined with periodical urine examinations. Within the last few years numerous quantitative tests for sugar in urine have been put on the market, but all are based on the principle of titration and operate as follows: A given amount of copper sulphate in an alkaline solution is boiled, and then urine which contains sugar is added drop by drop. The sugar. of the urine when boiled with the reagent oxidizes the copper sulphate into red or yellow cuprous oxide and thereby causes the blue color of the copper sulphate solution to gradually disappear. When the last trace of blue color disappears we can calculate by the amount of copper sulphate in the reagent, and the amount of urine required to discolor the reagent, the percentage of sugar present in the urine, as a definite amount of sugar will always oxidize the same amount of copper sulphate. There are different reagents, such as Benedicts, Fehlings, etc. but the princi ple is essentially the same.

All of these methods have certain serious inconveniences. First of all they require very much time. One has to put the urine in drop by drop and watch for the discoloration, as sometimes it takes a minute and a half for each drop to oxidize the copper sulphate. A test, to be properly performed may require from twenty minutes to a half hour. Second, the end point discoloration 4 is very indefinite and it is usually necessary to put in a few extra drops of urine to be sure that all the copper sulphate has been oxidized, thus making-the exactness of the test inaccurate. 7 And third, when the urine contains very much sugar it must be greatly Application filed August 15, 1929. Serial No. 386,232

diluted with water, as one drop extra of such urine would cause too great an inaccuracy. But even with the diluted urine we have a great inaccuracy, because by diluting the urine we also multiply the possibility of mistake in the end point discoloration by' the number of times the urine has beendiluted.

The object of the present invention is to provide a sim 1e, accurate and rapid quantitative test or sugar, particularly sugar in urine, so that the general practitioner can apply it in his oflice and the diabetic patient in his home, and so be able to adjust properly the diet and the amount of insulin required.

The method of the present invention is not one of titration, but a method which employs a colorimetric scale which enables us to know the exact quantity of sugar present, while we are doing aqualitative test. We know that copper sulphate in an alkaline solution is reduced by diabetic urine to red or yellow cuprous oxide. Urine with little sugar will give a yellow precipitate, but the precipitate will be red if the urine contains a large amount of sugar. The difference in the color of the precipitates is due to creatinine and protective colloids of the urine, in whose presence all of the copper oxide formed is of the yellow variety. We can thus prevent experimentally the formation of red cuprous oxide when large amounts of sugar in the urine are present, by adding to our reagent a certain amount of creatinine and a hydrophile collodial substance, such as acacia or India gum. Taking into consideration the fact that a given amount of glucose will always produce the same amount of yellow cuprous'oxide and that a 85 fixed amount of blue copper sulphate mixed with varying amounts of yellow cuprous oxide will give different shades of green, we can make a scale of green colors, each corresponding to a definite percentage of sugar.

In performing the test I employ the following two standard test solutions which I shall designate as reagents Nos. 1 and 2.

Reagent N 0. J

Grams or c. c. Copper sulphate 5. 00 Sodium citrate 250. 00 Sodium carbonate (anhydrous) 150. 00

Acacia ten percent sol 4. 00 Distilled water to make 1,000. 00

Reagent N0. 2

Creatinine four tenths percent sol 10.00

Acacia ten percent sol 10. 00

I also employ two color charts, one for small quantities of sugar, and one for larger quantities. These color charts each comprise a series of colors ranging from blue through green to yellow, the shades being empirically determined.

The technic of the test is as follows: To five c. c. of reagent No. 1 in a test tube add 0.5 0.0. of urine. (For convenience I employ a specially marked dropper forthis purpose.) Heat the solutlon in boiling water for well. If there is no cloudiness and no change in the original blue color, there is no sugar, but if the solution gets opaque and changes color, there is sugar present.

To determine the amount of sugar, compare the test tube with the color scale of the first chart and read the percentage of sugar corresponding to that color, these percentages ranging from one tenth per centto one and three quarters per cent. If the solution takes on a reddish yellow or red color, this indicates that a higher amount of sugar is present. In this case take again five c. c. of reagent No. 1 and add 0.12 c. c. of urine. But as there is not enough creatinine and colloidal substance in such a small amount of urine to prevent the formation of red cuprous oxide a red precipitate may form and therefore we also add 0.12 c. c. of reagent N0. 2 which makes the cuprous oxide yellow. Heat the mixture in boiling water for five minutes, let it cool, shake well and compare with color scale of the second chart and read the corresponding percentage of sugar. The percentages on this second chart range from two per cent to eight per cent.

This method, which is simple and accu rate, and can be very quickly performed has been verified by hundreds of tests with polariscope and Benedicts original quantitative method. It gives a percentage of error of less than one tenth per cent in urine containing up to two per cent sugar and of less than one half per cent in urine containing from two per cent to seven per cent sugar. Such a degree of accuracy is more than adequate for practical purposes. In very rare cases where there is more than five minutes, let it cool and shake eight per cent of sugar (a red precipitate forming after the second test), we can dilute the urine by two and perform the second test again with the diluted urine and multiply the percentage of the second chart by two.

This application is a continuation in part of my co-pending application Serial No. 268,082 filed April 6, 1928.

I claim:

1. The method of quantitatively determining sugar which comprises adding a known quantity of a sugar solution to be tested to a known quantity of a standard alkaline solution of copper sulphate, heat ing the mixture thereby reducing the copper sulphate to yellow cuprous oxide and changing the color of the solution from blue to green or yellow, the resultant color depending upon the amount of cuprous oxide formed, this in turn being a factor of the amount of sugar in the solution, and comparing this color with a standard color chart the graded colors of which correspond to definite percentages of sugar in the solution.

2. The method of quantitatively determining sugar as claimed in claim 1 which comprises adding a substance to the copper sulphate solution which prevents the formation of red cuprous oxide during the reduction.

The method of quantitatively determining sugar in urine which comprises adding a known quantity of the urine to be tested to a known quantity of a standard alkaline solution of copper sulphate, heating the mixture whereby any sugar present reduces the copper sulphate to yellow cuprous oxide and changes the color of the solution from blue to green or yellow, the resulting color depending upon the amount of cuprous oxide present, which in turn varies directly with the amount of sugar in the urine and comparing this color with a standard color chart, the graded colors of which correspond to a definite percentage of sugar in the urine.

4. The method of quantitatively determining sugar in urine as claimed in claim 3 which comprises adding creatinine and a hydrophile colloid to the copper sulphate solution to prevent the formation of red cuprous oxide during the reduction.

5. A test solution for use in quantitatively determining sugar which comprises an aqueous solution of copper sulphate, an alkali metal citrate, and an alkali metal carbonate to make the solution alkaline.

6. A test solution for use in quantitatively determining sugar which comprises an aqueous solution of copper sulphate, an alkali metal citrate, an alkali metal carbonate to make the solution alkaline and a substance preventing the formation of red cuprous oxid 7 determining su ar'which comprises an aqueous solution 0 copper sulphate, an alkali metal citrate, an alkali metal carbonate to make the solution alkaline and creatinine and a hydrophile colloid.

8. For use with a color scale, to determine the percentage of sugar in urine, a reagent having the property of changing color when heated with urine containing various amounts of sugar, said reagent consisting of the following substances dissolved in water; copper sulphate, an alkali metal citrate, an alkali metal carbonate, to make the solution alkaline, and a hydrophile colloidal substance and creatinine to make the color of the precipitated cuprous oxide yellow.

, having the property of changing to differ- 9. For u se'with a color scale, to determine the percentage of sugar in urine, a reagent ent colors when heated with urine containing various amounts of sugar, said reagent consisting of the following substances; copper, sulphate, sodium citrate, sodium carbonate, creatinine and acacia and distilled water.

10. For use with a color scale, to determine the percentage of sugar in urine, a reagent having the property of changing to differentcolors, when heated with urine containing various amounts of sugar, said reagent consisting of; copper sulphate, an alkali metal citrate, an alkali metal carbonate, creatinine and a hydrophile colloidal substance and water. i

11. For use with a color scale, to determine the percentage of sugar in urine, a reagent having the property of changing to difi'erent colors, when heated with urine containing Various amounts ofsugar, said re-, agent consisting of; copper sulphate, an alkali metal citrate, an alkali metal carbonate and water.

12. A test "solution for use in quantitatively determining sugar in urine which comprises copper sulphate, sodium citrate, sodium carbonate,'acacia and water in substantially the following proportions:

Copper sulphate 25. 00 grams ,Sodium citrate 250. 00 grams Sodium carbonate (anhydrous% 150. 00 grams Acacia en per cent $01..... 4. 0'0 c.c.

Distilled water to make 1, 000.00 c.c.

13., A test solution asclaimed in claim 12 A including a substance preventing the fprmation of red cuprous oxide. 7 v

14. A test solution as claimed in claiml2 including creatinine and a hydrophile colloidal substance.

In testimony whereof I afiix my signature.

ABRAHAM G. SHEFTEL.

A test solution for use in quantitatively 

